Apparatus for sampling particulate clouds



Jan. 16, 1951 K. R. MAY

APPARATUS FOR SAMPLING PARTICULATE CLOUDS Filed Feb. '7, 1946 FIG. 3. 37

2; Invent-or KENNETg Rowumvn 'MAY Attorneys Patented Jan. 16, 1951 APPARATUS FOR SAMPLING PARTICULATE CLOUDS Kenneth Rowland May, Cannanore, South India,

assignor to the Minister of Supply in His Majestys Government of the United Kingdom of Great Britain and Northern Ireland, London,

England Application February 7, 1946, Serial No. 646,039 In Great Britain July 18, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires July 18, 1964 19 Claims.

The present invention relates to apparatus for sampling or treating solid and liquid particulate clouds, with the aim of furnishing information.

on the concentration, state and size distribution of the particles, or of filtering such particulate clouds.

The main object of the invention is to provide an instrument which is capable of sampling a particulate laden gas such, for example, as wind borne particulate clouds, in which the particle size range is large, extending for example from 1 micron to 200 microns. Apparatus for this purpose proposed hitherto have been effective only over a small range of particle size, and to cover this wide range would have required the use of more than one instrument of different pe.

The apparatus accordin to the present invention comprises a plurality of jets, each having its mouth terminating adjacent to and directed towards a face of a sampling or like plate upon which impinges a particulate laden gas passing through the jet, the jets being disposed to cause the particulate laden gas to pass in succession through each of the jets, the mouths of which are successively of reduced size. By reducing the sizes of the mouths of the jets progressively of the series of jets, the speed or velocity of the gas through the jets and, in consequence, the efficiency of impaction of the particles on sampling plates is increased from jet to jet, with the result that the sampling plates show a gradation of particle size covering the range sampled. This size gradation is of great value and provides a short cut to estimating the size distribution of the cloud. Preferably the distance between each jet and its plate diminishes from jet to jet.

The invention is illustrated by way of example in the accompanying drawing in which Figure 1 is an end view of one form of sampling apparatus with a cap removed to show the interior of one tube, and

Figure 2 is a section on the line II-II, in Figure 1.

Figure 3 is a longitudinal section of a modified construction of apparatus.

Figure 4 is a perspective view of a jet used in the apparatus shown in Figure 3.

As shown in Figures 1 and 2 of the drawing, the instrument consists of four brass sampling tubes 3, 2, 3 and 4 of a bore slightly greater than 1 inch, the length of the first tube I being about 3 inches and that of the other three tubes 2, 3 and 4, about 1 inches. A sampling plate 5 is disposed longitudinally of the tube 1 and consists of a standard 3" x 1" microscope slide:

whilst sampling plates 6, T and 8 are respectively arranged in the tubes 2, 3 and 4, such plates being approximately half the size of the plate 5. Each plate is mounted in its tube so that it lies in the plane containing the axis of the tube, the plates resting against strips of metal 9 soldered to the inside of the tube, and being retained in position by leaf springs ID in such a manner that it is easily removable. Access to the plates is gained by a cap ll CIOSlIlg one end of each tube, these caps being a sliding and airtight fit on the tubes.

The first jet, or inlet orifice I2, is in the wall of the first tube l opposite the lower part of one face of the plate 5, the shape and position of the jet being chosen to fulfil the requirements of sampling in a wind. This jet has substantially parallel sides, the uter ends of which are sharpened to a knife edge. In cross-section it is roughly rectangular, the lower edge of the rectangle being outwardly convex instead of straight and the corners of the rectangle being rounded instead of sharp. This particular shape is of considerable importance as it' effectively compensates for end efiects of the trace on the first plate and therefore assists in enabling a reliable count across the plate to be obtained. The cross-section of this jet is 19 mm. wide and 6 mm. deep at the edges, increasing to 7 mm. at the centre, the radius of curvature of the convex side being approximately 45 mm.

A jet l3 connects the tube I to the tube 2 and secures them together at right angles. It is soldered at one end to the open end of the tube I, forming in effect a coninuation of this tube, and tapers down until the cross section of its mouth is a rectangle 14 mm. wide by 1.6 mm. deep. The tapered end protrudes into the tube 2 opposite the centre of one face of its sampling plate 6. In a similar way a jet I4 connects the tube 2 to the tube 3 and terminates adjacent the sampling plate 1, and a jet I5 connects the tube 3 to the tube 4 and terminates adjacent the sampling plate 8. The axes of the jets l2, l3, l4 and 15 are at right angles to the adjacent faces of the sampling plates 5, 6, 1 and 8 respectively. The dimensions of the mouth of the jet M are 14 mm. x 1 mm. and of the jet l5 are 14 mm. x 0.6 mm. Means for creating a flow of laden air through the jets is afforded in that the tube 4 is provided with an outlet l6 which can be connected by a tube IT to an external source of suction shown diagrammatically at lla. so that air or other laden gas can be drawn in succession through all four tubes at a constant rate. The velocity of the air or other laden gas through the jets will increase from jet to jet owing to their increasing fineness, and with the dimensions quoted above and with a rate of flow of 17 litres per minute this velocity will be approximately 5 M. P. H. for the jet |2, 30 M. P. H. for the jet H, 50 M. P. H. for the jet Hi and 80 M. P. H. for the jet l5. As a result the efiiciency of impaction of the particles on the sampling plates will increase from jet to jet so that the cloud will be sorted out into fairly well defined size groups on each plate. The approximate range of sizes of the liquid particles deposited on the four plates is as follows: On the first plate 5, greater than microns; on the second plate 6, -30 microns; on the third plate '71 micron; and on the fourth plate 8, 3-0.5 micron. There is thus some overlap from plate to plate but an important feature of the instrument is that after a little experience it is possible to obtain a good idea of the size distribution of the particles in the cloud by a mere glance at the relative density of the deposits on the plates.

The distance between the mouth of each jet and the plate adjacent thereto diminishes from jet to jet. The first two jets have the side which is furthest from the succeeding jet continued until it almost touches the sampling plate. This forces the major part of the airflow to proceed towards the next jet and prevents particles or droplets being lost in the dead space at the cap end of each tube. This precaution is unnecessary with the third and fourth jets owing to their small distance from the plates. Furthermore, although the axes of successive tubes are shown at right angles to one another, they can be arranged with their axes at any other angle found suitable for the purpose required.

The sampling plates are coated with a suitable detecting r sticky medium or in some cases are left plain, the treatment of the plates depending upon the nature of the particles or droplets. A full discussion of this treatment is outside the scope of the present description, as the technique of treating the plates and the methods of obtaining information from the deposits thereon form no part of the present invention.

A modified construction of apparatus is illustrated in Figures 3 and 4 in which jets are housed in cylinders formed in a single block. As shown,

a block 28 of suitable material, e. g. brass, has

formed therein three cylinders 2|, 22 and 23 with their axes parallel to one another. The lower part of each cylinder is of less diameter than its upper part so that an annular shoulder E i is formed in each cylinder .upon which a jet, in-

sorted into the cylinder can rest. A port 25 connects the upper ends of the cylinders 2| and 22, a similar port 26 connects the upper ends of the cylinders 22 and 23, whilst a port 21 connects the upper end of the cylinder 23 with a gas outlet 28. A suitable source of suction, shown diagrammatically at 26a, can be connected to gas outlet 28 so that air or other laden gas can be drawn through the apparatus. The lower part of each cylinder is provided with a longitudinally extending channel 23 which leads respectively to the ports 25, 26 and 27. The upper ends of the cylinders are closed by a cover plate 30 to which is secured a gas inlet 3|, whilst the lower ends of the cylinders are closed by a suitable plate or slide 32. Gasket rings 33, housed in annular recesses about the lower ends of the cylinders 2|, 22 and 23, provide a gas tight joint between the block 20 and the plate or slide 32 to prevent the escape of gas from the lower ends of the cylinders between the block and the plate or slide. A jet 3% housed in the cylinder 2| comprises a head portion or part of larger diameter located in the upper part of the cylinder and a part of smaller diameter located in the lower part of the cylinder, a bore extending longitudinally of the jet being in communication with the gas inlet 3|. Housed in the cylinder 22 is a jet 36 consisting of two parts f different diameters, the head or part of larger diameter being located in the upper part of the cylinder 22 and resting on its annular shoulder 24, whilst the part of smaller diameter depends from the part of greater diameter and is located in the lower part of the cylinder 22. The part of the jet of smaller diameter has a bore which, at its upper end, enters a radially disposed channel 31 in the head or part of the jet of larger diameter, the said head or part of the jet of larger diameter also having therein a groove 38 which is located diametrically opposite the channel Bl. The jet 36 is so positioned in the cylinder 22 that its channel 3'! is in register with the port 25 and its groove 38 is in register with the port 26. A jet 39, similar in construction to the jet 36 is located in the cylinder 23, a radially disposed channel 40 therein being in register with the port 26 whilst a groove 4| is in register with the port 21.

The orifices of the jets 34, 36 and 39 are progressively smaller in size and terminate progressively nearer the plate or slide 32, the gas issuing from the orifice of each jet being directed towards the plate or slide so that it impinges upon that part of the said plate or slide in register with the lower end of the cylinder in which the jet is located.

In operation gas passes from the gas inlet 3|, through the jet 34, impinges upon the plate or slide 32 and then passes upwardly, a part of the stream of gas passing along the'channel 29 in the cylinder 2|, through the groove 35 and the port 25 intothe channel 37 of the jet 36 and through the said jet to impinge again upon the plate or slide 32. In a similar manner the stream of gas passes upwardly, through the port 26 and the jet 46 to impinge for a third time upon the plate or slide 32 and thence upwardly to the port 21 from which it flows through the gas outlet. The plate or slide 32 has therefore three localised areas that have been subject to contact with gas flowing at different velocities due to the progressive diminution of the orifices of the jets 34, 36 and 39.

The apparatus according to this invention is primarily intended for sampling clouds of chemical warfare agents, but it has many other obvious applications. For example, it has been employed for determining the size distribution of droplets in sprays of all kinds, including those employed for humidifi'cation, for allaying dust and other filtering operations, and for destroying insects and pests. In meteorology it has been employed for estimating fogs and mists, and it may also be useful for sampling coarse industrial suspensions.

Obviously, the number of tubes or cylinders employed and the sizes of the jet orifices can be varied from those stated above, according to the nature of the medium treated and of the use made of the apparatus. Moreover the housing for the jets can be of any desired cross section, e. g. elliptical or square.

What I claim is:

1. An apparatus for sampling particulate clouds, comprising a series of jets with mouths successively of reduced size, a sampling plate adjacentthe mouth of each jet and towards which the jetis directed, and means for causing a flow of particulate laden gas in succession through the jets.

2. An apparatus for sampling particulate clouds, comprising a series of chambers provided withinlets and outlets and connected in series, a sampling plate mounted in each chamber, a series of jets with mouths that are successively of re duced size, each jet beingconnected to the outlet of one chamber and to the inlet of the next chamber of the series with its mouth directed towards the sampling plate in-said chamber and means for connecting the outlet of the ultimate chamber to a source of suction.

3. An apparatus for sampling particulate clouds, comprising a series of chambers provided with inlets and outlets and connected in series, a sampling plate mounted in each chamber, a series of jets with rectangular mouths that are successively of reduced size, each jet being connected to the outlet of one chamber and to the inlet of the next chamber of the series with its mouth directed towards the sampling plate in said chamber, and means for connecting the outlet of the ultimate chamber to a source of suction.

4. An apparatus for sampling particulate olouds, comprising a series of chambers provided with inlets and outlets and connected in series, a sampling plate mounted in each chamber, a series of jets with rectangular mouths that are successively of reduced size, each jet being connected to the outlet of one chamber and to the inlet of the next chamber of the series with its mouth directed towards the sampling plate in said chamber, the mouths of the jets being successively nearer the sampling plate, and means for connecting the outlet of the ultimate chamber with a source of suction.

5. .An apparatus for sampling particulate clouds, comprising a series of tubes with inlets, a cap closing one end of each tube, a jet forming a continuation of the open end of each tube and extending into the inlet of the next tube of the se ries, the mouths of the series of jets being successivelyof reduced size, a sampling plate mounted in each tube with its face at right angles to the axis of the inserted jet, an outlet communicating with the ultimate tube of the series, and means for conveying gases through the tubes and the jets in succession.

6. An apparatus for sampling particulate clouds, comprising a series of tubes with inlets, a cap closing one end of each tube, ajet forming a continuation of the open end of each tube and extending into the inlet of the next tube of the series, a sampling plate mounted in and extending longitudinally of each tube, the mouths ofrthe jets being directed towards the faces of the sampling plates and being successively of reduced size, an outlet communicating with the ultimate tube of the series, and means for conveying gases through the tubes and the jets in succession.

'7. An apparatus for sampling particulate clouds, comprising a series of tubes with inlets, a cap closing one end of each tube, a jet forming a continuation of the open end of each tube and extending into the inlet of the next tube of the series, 'a sampling plate mounted in and extending means for conveying gases through the tubes and theijets insuccession.

8. An apparatus for sampling particulate clouds, comprising a series of tubes with inlets, a cap closing one endof each tube, a jet forming a continuation of the open end of each tube and extending into the inlet of the next tube of the series, a sampling plate mounted in and extending longitudinally of each tube and means for connecting the ultimate tube of the series with a source of suction, the mouths of the said jets being directed towards the faces of the sampling plates and being successively of reduced size and nearer to a sampling plate.

9. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders in parallel relationship, a cover plate mounted on one face of the body member to close one end of each cylinder, at sampling plate mounted on the opposite face of the body member to close the other end of each cylinder, a jet in each cylinder with its mouth .directed towards the sampling plate, an inlet connected to the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

10. An apparatus for sampling particulate clouds, comprising a body memberhaving therein a series of cylinders in. parallel relationship, a cover platemounted on one face of the body member to close one end of each cylinder, a sampling plate mounted on the opposite .face of the body member to close the other end of each cylinder, a jet in each cylinder with its mouth directed towards the sampling plate, the mouths of said jets being progressively smaller in size in each successive cylinder of the series, an inlet connected to the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

11. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders in parallel relationship, a cover plate on one face of the body member to close one end of each cylinder, a sampling plate on the opposite face of the body member to close the other end of each cylinder, a jet in each cylin der with its mouth directed towards the sampling plate, theimouths of said jets being progressively smaller in size and nearer the sampling plate in each successive cylinder of the series, an inlet connected to the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

12. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders in parallel relationship, a cover plate on one face of the body member to close one end of each cylinder, a sampling plate on the opposite face cf'the hodymember to close the other end of each cylinder, a gasket :ring around the mouth of each cylinder adjacent the sampling plate, a jet in each cylinder with its mouth directed towards the sampling plate, the mouths of the said jets being progressively-smaller in size and nearer the sampling plate in .eachsuccessive cylinder of the series, an inlet connected to the jet in thelfirst'of the seriesof cylindersan outlet communicating with the last of the .series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

13. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders in parallel relationship, a cover plate on one face of the body member to close one end of each cylinder, a sampling plate on the opposite face of the body member to close the other end of each cylinder, a gasket ring around the mouth of each cylinder adjacent the sampling plate, an annular shoulder in each cylinder, a jet in each cylinder supported upon said annular shoulder with its mouth directed towards the sampling plate, the mouths of said jet being progressively smaller in siZe and nearer the sampling plate in each successive cylinder of the series, an inlet connected to the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

14. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders and ports connecting successive cylinders at one end thereof, means for closing the ends of the cylinders adjacent said ports, a sampling plate closing the other end of each cylinder, a jet in each cylinder directed towards the sampling plate, a head on each jet having passages connecting the ports leading from the prior cylinder and leading to the next cylinder of the series respectively to the bore of the jet and to the underside face of the jet head, an inlet connected to the bore of the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

15. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders and ports connecting successive cylinders at one end ther of, means for closing the ends of the cylinders adjacent said ports, a sampling plate closing the other end of each cylinder, a jet in each cylinder directed towards the sampling plate, the mouths of said jets being progressively smaller in each successive cylinder of the series, a head on each jet having passages connecting the port leading from the prior cylinder and leading to the next cylinder of the series respectively to the bore of the jet and to the underside of the jet head, an inlet connected to the bore of the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

16. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders and ports connecting successive cylinders at one end thereof, means for closing the ends of the cylinders adjacent said ports, a sampling plate closing the other end of each cylinder, a gasket ring around the mouth of each cylinder adjacent the sampling plate, a jet in each cylinder directed towards the sampling plate, the mouths of said jets being progressively smaller in each successive cylinder of the series, a head on each je having passages connecting the ports leading from the prior cylinder and leading to the next cylinder of the series respectively to the bore of the jet and to the underside of the jet head, an inlet connected to the bore of the jet in the first of the series of cylinders, an

outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

17. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders and ports connecting successive cylinders at one end thereof, means for closing the ends of the cylinders adjacent said ports, a sampling plate closing the other end of each cylinder, a gasket ring around the mouth of each. cylinder adjacent the sampling plate, a. jet in each cylinder directed towards the sampling plate, the mouths of said jets being progressively smaller and nearer the sampling plate in each successive cylinder of the series, a head on each jet having passages connecting the port leading from the prior cylinder and leading to the next cylinder of the series respectively to the bore of the jet and to the underside of the jet head, an inlet connected to the bore of the jet in the first of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for conveying gases from each cylinder to the jet in the next cylinder of the series.

18. An apparatus for sampling particulate clouds, comprising a body member having therein a series of cylinders and ports connecting successive cylinders at one end thereof, an annular shoulder in each cylinder, means for closing the ends. of the cylinders adjacent aid ports, a sampling plate closing the other end of each cylinder, a gasket ring around the mouth of each cylinder adjacent the sampling plate, a jet in each cylinder directed towards the sampling plate, the mouths of said jets being progressively smaller and nearer the sampling plate in each successive cylinder of the series, a head on each jet, resting on the annular shoulder and having passages con.- necting the port leading from the prior cylinder and leading to the next cylinder of the series, respectively to the bore of the jet and to the underside of the jet head, an inlet connected to the bore of the jet in the first cylinder of the series of cylinders, an outlet communicating with the last of the series of cylinders, and means for convey ing gases from each cylinder to the jet in the next cylinder of the series.

19. An apparatus for sampling particulate clouds, comprising a series of tubes, an inlet in the side wall of each tube, a cap closing one end of each tube, a jet forming a continuation of the opposite end of each tube and extending into the inlet of the next tube of the series, a sampling plate mounted in and extending longitudinally of each tube, said jets being directed towards the faces of the corresponding sampling plates, said caps being removable to provide access to said plates, an outlet communicating with the ultimate tube of the series, and means for conveying gases through the tubes and the jets in succession.

KENNETH ROWLAND MAY.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,274,415 Hill Aug. 6, 1918 1,416,089 Hedberg May 16, 1922 2,034,185 Haultain Mar. 17, 1936 

1. AN APPARATUS FOR SAMPLING PARTICULATE CLOUDS, COMPRISING A SERIES OF JETS WITH MOUTHS SUCCESSIVELY OF REDUCED SIZE, A SAMPLING PLATE ADJACENT THE MOUTH OF EACH JET AND TOWARDS WHICH THE JET IS DIRECTED, AND MEANS FOR CAUSING A FLOW OF 